The Imaging Core facility will service the program in the area of light microscope imaging and analysis. The core is built around the state-of- the-art facility available in the Nephrology Division of the Department of Medicine, and benefits from the experience of key core personnel in the application of imaging methodologies to the analysis of hematopoietic cell function. The facility is currently equipped with two confocal laser-scanning microscopes: a Zeiss LSM 510 capable of UV excitation of fluorescence; and a BioRad MRC-1024 with Ti: sapphire laser capable of 2-photon excitation as well as Kr/Ar laser for conventional confocal imaging. Two wide-field microscope stands equipped with cooled CCD cameras are available: an Applied Precision Deltavision system optimized for image deconvolution; and a second Nikon stand used for motility assays. Stage incubators with CO2 perfusion are available for maintaining and imaging live cells on the stage of the microscope for long periods. Computing resources available include workstations with software for image processing, image deconvolution, rendering of 3-D image volumes and quantitative analysis of image data. The aim of the imaging core is to provide 1) technology and expertise in imaging live hematopoietic cells by transmission light microscopy and fluorescence microscopy to facilitate real-time analysis of signaling events and Rac2 dependent processes; and 2) expertise and support for quantitative analysis of image data generated by fluorescence microscopy to complement biochemical and other analysis of hematopoietic cell function.